In various types of communications systems, it is desirable to increase the available bandwidth by means of isolating the R.F. beams received/transmitted by the receiving/transmitting antenna system. Two prominent techniques which are currently used to achieve this desired beam isolation in these antenna systems are, spatial and polarization isolation of the beams. The need for high antenna gain and high system bandwidth is particularly acute in communications systems which provide thousands of independent communications channels with high efficiency and minimum intermodulation distortion and channel cross-talk.
Furthermore, there are other antenna systems which are configured to serve multiple functions which require signals of different polarizations, e.g., antenna systems employed in spaceborne satellites designed to simultaneously perform surveillance and meteorological and/or astronomical observation functions.
Accordingly, it can be appreciated that, in certain instances, it is desirable to have an antenna system which is capable of simultaneously transmitting and/or receiving separate R.F. beams of linear and circular polarizations. In this connection, presently available antenna systems require the utilization of separate antenna feed networks and separate antennas in order to be rendered capable of simultaneously transmitting and/or receiving separate R.F. signals of linear and circular polarizations. In some instances, it is even more desireable to have an antenna system which is capable of simultaneously transmitting and/or receiving separate R.F. signals of orthogonal linear polarizations, and separate R.F. signals of opposite-sense circular polarizations. In this connection, although it is within the state-of-the-art to feed either separate orthogonally linear polarized R.F. signals or separate opposite-sense circularly polarized R.F. signals through a common antenna feed network, it is not within the present state-of-the-art to feed both separate orthogonally linear polarized R.F. signals and separate opposite-sense circularly polarized R.F. signals through a common antenna feed network. Rather, in these current state-of-the-art antenna systems, it is necessary to utilize separate antennas and separate antenna feed networks for each of the above-identified R.F. signal pairs. Of course, for reasons of cost and weight economy, it would be highly advantageous to have available an antenna system which requires only a single antenna and a single antenna feed network for both of the above-identified R.F. signal pairs.
The present invention is directed to providing such a highly advantageous antenna system.